I reached 75 nights and my choice of more SNAs (took 5 when I reached 50 nights) or a free 35k point night (actually 40k but my reservations are all at 35k). I got a nice suite upgrade in Madrid last month and the hotels coming up all have nice suite choices.
I feel the SNAs are a better "experience" choice as getting another 35k points isn't that difficult.
What do other Insiders think? What are your preferences?